579. Onassis v Vergottis [1968] 2 Lloyd’s Rep. 403, 431

Per Lord Pearce:

“… Credibility involves wider problems than mere “demeanour” which is mostly concerned with whether the witness appears to be telling the truth as he now believes it to be.

Credibility covers the following problems. First, is the witness a truthful or untruthful person? Secondly, is he, though a truthful person, telling something less than the truth on this issue, or, though an untruthful person, telling the truth on this issue? Thirdly, though he is a truthful person telling the truth as he sees it, did he register the intentions of the conversation correctly and, if so, has his memory correctly retained them?

Also, has his recollection been subsequently altered by unconscious bias or wishful thinking or by overmuch discussion of it with others?

Witnesses, especially those who are emotional, who think that they are morally in the right, tend very easily and unconsciously to conjure up a legal right that did not exist.

It is a truism, often used in accident cases, that with every day that passes the memory becomes fainter and the imagination becomes more active. For that reason a witness, however honest, rarely persuades a Judge that his present recollection is preferable to that which was taken down in writing immediately after the accident occurred.

Therefore, contemporary documents are always of the utmost importance.

And lastly, although the honest witness believes he heard or saw this or that, is it so improbable that it is on balance more likely that he was mistaken? On this point it is essential that the balance of probability is put correctly into the scales in weighing the credibility of a witness, and motive is one aspect of probability.

All these problems compendiously are entailed when a Judge assesses the credibility of a witness; they are all part of one judicial process and in the process contemporary documents and admitted or incontrovertible facts and probabilities must play their proper part …”